Power can be wirelessly conveyed from one place to another using the Faraday effect, whereby a changing magnetic field causes an electrical current to flow in an electrically isolated secondary circuit. A form of wireless power transfer (WPT) currently in use involves magnetic inductive charging. One form of magnetic inductive charging is shown in WPT system 10 of FIG. 1. The FIG. 1 WPT system 10 comprises two coils 12, 14 in close proximity but separated by an air gap 16. One coil 12 of WPT system 10 acts as a wireless power transmitter and the other coil 14 acts as the receiver of wireless power. A time-varying current flows in transmitter coil 12, which produces a time-varying magnetic field (shown as flux lines in FIG. 1). This time-varying magnetic field induces current in the nearby receiver coil 14 (Faraday's law), which can then be used to charge various devices (not shown) which may be electrically connected to receiver coil 14.
In PCT application No. PCT/CA2010/000252 (published under WO/2010/096917), a magnetic-coupling technology has been described to provide a number of viable WPT systems that can be used to charge, by way of non-limiting example, batteries generally, electric (e.g. battery operated) vehicles, auxiliary batteries, electric (e.g. battery operated) buses, golf carts, delivery vehicles, boats, drones, trucks and/or the like. FIG. 2 schematically depicts a WPT system 20 incorporating a magnetic-coupling technology of the type described in PCT/CA2010/000252. WPT system 20 comprises a wireless magnetic power transmitter 22 and a wireless magnetic power receiver 24 separated by an air gap 26. The power transfer in WPT system 20 is via rotational magnetic coupling rather than via direct magnetic induction. In the FIG. 2 WPT system 20, transmitter 22 comprises a permanent magnet 22A and receiver 24 comprises a permanent magnet 24A. Transmitter magnet 22A is rotated (and/or pivoted) about axis 28. The magnetically coupled permanent magnets 22A, 24A interact with one another (magnetic poles represented by an arrow with notations of “N” for north and “S” for south in FIG. 2), such that movement of transmitter magnet 22A about axis causes corresponding movement (e.g. rotation and/or pivotal movement) of receiver magnet 24A about axis 27. The time-varying magnetic fields generated by rotating/pivoting magnets 22A, 24A of WPT system 20 typically has a lower frequency compared to WPT systems based on magnetic induction. The FIG. 2 WPT system 20 transfers power most effectively when there is strong coupling between rotating/pivoting magnets 22A, 24A.
A challenge faced by WPT systems is the alignment of the WPT transmitter and WPT receiver. When the WPT transmitter and WPT receiver are misaligned, the power transfer process loses efficiency—i.e. it takes longer to transfer a given amount of power/charge. In some cases, where misalignment is extreme, power transfer may be ineffective—i.e. no measurable power/charge transfer occurs. Alignment of the WPT transmitter and WPT receiver can be difficult, for example, in automotive applications (e.g. for charging a vehicle battery). In such applications, the WPT receiver is typically located on the underside of a vehicle (e.g. out of view of the driver of the vehicle) and a WPT transmitter is located on the ground. In such circumstances, alignment of the WPT transmitter and WPT receiver can be difficult and can reduce power transfer efficiency and/or efficacy. A number of factors can exacerbate the challenges associated with alignment of the WPT transmitters and WPT receivers. For example, such exacerbating factors may include the relatively small size of the WPT transmitters/receivers, vehicle to vehicle dimensional variations and limited capacity for the vehicle driver to see the WPT receiver and/or the WPT transmitter.
The foregoing examples of the related art and limitations related thereto are intended to be illustrative and not exclusive. Other limitations of the related art will become apparent to those of skill in the art upon a reading of the description and a study of the drawings.